1. Field of the Invention
The present invention relates to a method and apparatus for image forming capable of effectively removing residual toner from an image bearing member with a cleaning member having optimal degrees of hardness and repulsion elasticity, a cleaning mechanism used in the apparatus, a process cartridge including the cleaning mechanism in the apparatus, and toner used in the apparatus.
2. Discussion of the Background
Generally, an image forming apparatus employing an electrophotographic method includes an image bearing member, a charging mechanism, an optical writing mechanism, a developing mechanism, an image transfer mechanism, and a cleaning mechanism, and performs image forming operations as follows. The charging mechanism uniformly charges the image bearing member. The optical writing mechanism then irradiates the image bearing member to form an electrostatic latent image. The developing mechanism subsequently develops the electrostatic latent image to a toner image. The image transfer mechanism receives the toner image on an image transfer member or a recording medium conveyed by a transfer member, so that the toner image can be fixed in a fixing mechanism and be discharged to a discharging tray or the like. After the toner image is transferred to the image transfer mechanism, the cleaning mechanism removes toner remaining on the image bearing member.
The cleaning mechanism with respect to an image bearing member generally includes a blade cleaning method, a fur brush cleaning method, a magnet brush cleaning method, or the like. Generally, the blade cleaning method is used because of its small size and low cost.
Recently, color image forming apparatuses using the electrophotographic image forming method have been widely used, digitalized images are easily available, and printed images are required to have higher image definitions. While higher image resolution and gradient are studied, the toner visualizing the electrostatic latent image is studied to have further sphericity and smaller particle diameter to form high definition images. Since the toner prepared by pulverizing methods has a limit of these properties, polymerized toners prepared by suspension polymerizing methods, emulsification polymerizing methods, and dispersion polymerizing methods capable of conglobating the toner and making the toner have a small particle diameter are being used.
The small toner having a substantially spherical shape is known to have a poor cleaning ability. Since background image forming apparatuses have used a cleaning blade formed by a rubber material for removing the toner prepared by pulverizing methods, the cleaning blade cannot stop the toner from falling through a space between an image bearing member and the cleaning blade into an inside of the image forming apparatus. Any toner that falls through the space may cause further abrasion of the cleaning blade, which may result in a shorter life of the cleaning blade. The toner also may adhere to a charging roller of the charging mechanism, which may result in a toner filming to produce defect images. Reducing a coefficient of friction of an image bearing member may work to improve a margin of cleaning ability of the cleaning blade, but may not be sufficiently effective to prevent the toner from falling through the space between the image bearing member and the cleaning blade.
The coefficient of friction of the image bearing member may be reduced by including a fluorocarbon resin on the surface thereof so that durability can be increased and a curl of a leading edge of the cleaning blade can be prevented. However, the above-described image bearing member may not surely remove the toner having a degree of sphericity equal to or greater than 0.93.
Further, better cleaning ability may be obtained by mixing zinc stearate into a toner particle and applying zinc stearate to the image bearing member. However, there may be various restrictions due to a mixing ratio of zinc stearate and intervals of the application.